The present invention relates generally to air-driven means for continuously varying the direction of the stream of air from a duct outlet of a forced air heating or ventilation system. Air registers with air-driven oscillating louvers or other air stream deflecting means are known in the art, representative prior art devices being disclosed, for example, in U.S. Pat. No. 2,196,308 issued to F. Johnston on Apr. 9, 1940, U.S. Pat. No. 2,800,851, issued to J. Kronrad et al. on July 30, 1957, U.S. Pat. No. 3,242,846 issued to C. E. Bunn on Mar. 29, 1966, and U.S. Pat. No. 3,699,873 issued to A. H. Irvin on Oct. 24, 1972. However, each of these prior art devices utilizes a standard fan wheel with angled radial blades adapted to be operative in response to an air stream moving in a direction generally parallel to the axis of rotation of the fan wheel.
The maximum dimensions of such fan wheels are in a plane perpendicular to the direction of the air stream and, therefore, such fan wheels are not suitable for use in flat, narrow ducts. More particularly, such fan wheels could not be mounted in the standard home wall duct which has transverse dimensions of approximately 21/4 inches by 12 inches, with a maximum depth at the register outlet of 23/4 inches. In use, such ductwork is arranged with the 12-inch dimension parallel to the room wall, with the register opening being in the wall a slight distance above the floor, the shallow 21/4 -inch depth being necessary in order to permit the duct to be accommodated between the interior and exterior walls of the building. A standard fan blade of the type disclosed in the prior art, in order to be utilized in such a duct, would have to have a diameter of considerably less than 23/4 inches, since the louvers must also be accommodated in this 23/4-inch space. With the 100 cubic feet per minute airflow in the standard home heating system, a fan blade of such a small diameter would be insufficient to generate the power needed to drive the louvers.